Intervertebral discs are fibrous cartilage pads that allow the spine to bend and serve as “shock” absorbers for the vertebrae, absorbing pressure delivered to the spinal column. Additionally, they maintain the proper anatomical separation between two adjacent vertebras. This separation is necessary for allowing nerves to exit and enter unimpeded from the spinal column.
To alleviate the pain caused by a damaged disc, current treatment methods include a discectomy in which the affected intervertebral disc is removed and an interbody fusion implant is inserted. Thereafter, the two adjacent vertebral bodies can be fused together in a process commonly referred to as spinal fusion. The disc prosthesis restores the angular relationship between the adjacent vertebrae to be fused, and provides the material for bone growth to occur between the two vertebral bodies.
A large number of these interbody fusion implants have been developed. These implants act as artificial intervertebral discs and can include fusion cages made from metals and/or synthetic materials. Many prostheses can also be fashioned from allograft bone that is harvested from portions of long bone including the femur, humerus, tibia, fibula, ulna and radius.
Although the success or failure of the fusion can often depend upon the type and properties of the prosthesis that is placed between the adjacent vertebral bodies, the prosthesis must also remain fixed in the desired position so that the appropriate spacing and geometry of the spine can be maintained. Unfortunately, because of the continuous forces that act upon the vertebrae and especially the disc prosthesis there is a tendency for the prosthesis to migrate due to shifting, rotation or slippage. Obviously, such movement can result in pain to the patient and failure of the bone fusion.
To address this risk buttress staples have been developed to help hold the disk prosthesis in place. An example of the current state of the art in this field is disclosed in U.S. Pat. No. 7,341,591, the disclosure of which is incorporated herein by reference. Although these devices have had some success in mitigating the risk of disc slippage, they are relatively difficult to implant in a surgical setting, and rely almost entirely on the integrity of bone screws for stability. Accordingly, a need exists for a graft locking plate that provides greater ease of use and stability.